The use of rotatably driven abrasive articles is widespread and familiar in our industrial society. One of the more serious problems encountered in the use of such devices resides in the provision of effective means for preventing undesired or accidental disassociation of the article from the shaft, spindle or other rotatable drive means on which it is mounted. This problem is particularly acute when the connection between the article and its driving shaft or spindle is intentionally detachable to facilitate quick removal and replacement of the article. Into this category fall a host of devices, for example, portable powered grinders wherein the grinding wheels employed are intentionally detachable from the power driven shaft so that they may be readily replaced. To properly mount the grinding wheel upon the shaft, provision must be made to provide sufficient clamping force and also to secure the wheel rotationally.
One means of securing the grinding wheel to the drive shaft has been to provide an appropriate backing member with a central opening which is aligned with an opening provided in the depressed center abrasive grinding wheel. A bolt or nut member (depending upon the configuration of the drive shaft; that is, whether it is externally or internally threaded) is inserted from the face side of the grinding wheel and is then tightened in place. In this manner a plurality of loose parts are configured in a completed assembly ready for use. As the grinding wheel is utilized the appropriate clamping force is provided to securely affix the grinding wheel to the drive shaft. Such an assembly, however, typically requires appropriate tools such as wrenches or the like to attach and remove the grinding wheel from the drive shaft. Such a device is shown in U.S. Pat. Nos. 489,149; 3,596,415; 1,998,919; 566,883; 507,223; 1,162,970; 791,159; 489,149 and 3,210,892.
Subsequently it became desirable to affix the mounting hub permanently to the grinding wheel so that the entire unit may be attached and detached from the drive shaft and discarded when the grinding wheel has been worn down. In these types of devices it is customary to utilize an adhesive such as an epoxy resin or the like between the backing member and the back surface of the grinding wheel to retain integrity between the mounting hub and the grinding wheel to secure the wheel rotationally.
Even though the adhesive tended to work quite well in most applications, it was discovered that in some instances the adhesive would break loose and the grinding wheel would rotate relative to the mounting hub. Such was particularly the case since the hub was a one-piece member which was internally threaded and held in place upon the grinding wheel by swaging an extension thereof into place, thus providing a fixed clamping force holding the grinding wheel. No additional clamping force was exerted during further rotation of the wheel during use as was the case with the traditional nut which was secured from the face as above described. As a result various keyways and corresponding key structures were developed between the wheel and the mounting hub and used in conjunction with the adhesive to preclude rotational movement between the mounting hub and the grinding wheel. Examples of such devices are shown in U.S. Pat. Nos. 3,136,100; 4,015,371; 2,278,301; 3,081,584; 3,500,592; 3,800,483; 4,240,230 and 4,541,205.
Additional prior art patents known to applicant are U.S. Pat. Nos. 3,041,797; 3,879,178; 1,724,742; 3,912,411; 3,879,178; 3,960,516; 4,026,074; 4,054,425; 4,088,729; 4,322,920; 4,439,953; 4,449,329; 4,601,661; 791,791; 872,932; 2,567,782; 3,136,100; 3,210,892 and 3,621,621.
The devices utilized in the prior art for providing the disposable finishing article assembly including the permanent affixed mounting hub generally provide the service intended. There are, however, certain inherent disadvantages found with regard to the various devices. Such disadvantages are that in manufacturing, the utilization of an adhesive adds additional labor to the cost of manufacturing. In certain of the devices, parts must be keyed together and properly aligned in order to function appropriately. In addition thereto, through the utilization of die-cast mounting hubs which are included as an integral unitary part of the backing member there is no additional clamping force exerted upon the finishing article as it is being rotated by the power tool. Furthermore, such mounting hubs are relatively bulky, take up space and add substantial weight and additional cost to the completed product.
To solve the problems of the prior art as briefly summarized above, applicant has developed an abrasive article having a drive member non-removably affixed thereto for mounting on a rotatable spindle of a power tool. The drive member includes a backing member and a retaining nut positioned on opposite sides of the abrasive article with the retaining nut upset or swaged to hold the retaining nut and the backing member together on opposite sides of the abrasive article. A pressure cap is provided and may take various forms and may be constructed of different materials. For example, the pressure cap may be metal or plastic and may be secured to the backing member through a rotational mechanism or through upsetting or clamping the backing member. The pressure cap engages a shoulder on the spindle of the power tool and through engagement between the treads and the retaining nut and the threaded spindle as well as the forces applied by the pressure cap. The abrasive article is placed in compression between the backing member and a flange on the retaining nut during use of the abrasive article when such is operatively secured upon the spindle of the power tool. Such devices are illustrated and described in applicant's issued patents; namely 4,694,615; 4,754,577; 4,760,670; 4,924,634; 4,979,336 and 5,031,361. These patents of applicant constitute the best prior art known to applicant. The disclosure of applicant's U.S. Pat. No. 4,694,615 is incorporated herein by reference.